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Biomedical subjects

R T Brouillette

Publications and source records attributed to R T Brouillette.

At least 73 records · Page 4Linked to original sources
PubMed1985

Home pneumograms in normal infants.

To obtain age-specific normative data, we performed home cardiorespiratory recordings (pneumograms) in 56 normal infants at 1 month of age. A repeat pneumogram was performed at 3 months in 39 infants. Total sleep time was determined and all sleep intervals were summed and analyzed for five respiratory pattern variables: frequency of all apneic episodes greater than or equal to 6 seconds in duration (A6/D%), periodic breathing, longest apneic episode, and number of episodes greater than 11 and greater than 15 seconds. The normal infants at 1 and at 3 months were compared with 66 patients with apnea of infancy. Median A6/D% was 0.1 in the normal infants at 1 and 3 months, compared with 0.64 in those with apnea of infancy (P less than 0.001). Median periodic breathing was 0.4 and 0.2 episodes per 100 minutes in the normal infants at 1 and 3 months, respectively, compared with 1.25 in infants with apnea of infancy (P less than 0.001). Median longest apneic episode was 8.0 seconds in the normal infants at 1 and 3 months, compared with 11 seconds in those with apnea of infancy (P less than 0.001). No normal infant had an apneic episode greater than 15 seconds in duration, whereas the group with apnea of infancy had 0.4 +/- 1.0 episodes of apnea of greater than 15 seconds (P less than 0.01). Despite these significant group differences, use of these respiratory patterns either alone or in combination permitted only about 80% correct classification of normal infants and those with apnea of infancy.

Age Factors↗
PubMed1985

Effects of almitrine on hypoglossal and phrenic electroneurograms.

Almitrine increases breathing by stimulating peripheral chemoreceptors. Previous studies suggest clinical usefulness in the adult with chronic obstructive pulmonary disease, but little data are available to decide whether almitrine would be helpful in diseases involving pharyngeal airway obstruction, such as apnea of prematurity or obstructive sleep apnea. We investigated the effect of intravenous almitrine on hypoglossal (HG), an upper airway nerve, and phrenic (PHR) neural activity in eight alpha-chloralose-urethan anesthetized, paralyzed, vagotomized, and artificially ventilated cats. Recordings were made of raw and integrated HG and PHR electroneurograms (ENGs), alveolar PCO2, arterial PO2, arterial blood pressure, and rectal temperature. A dose-response study of cumulative almitrine doses ranging from 0.1 to 4.0 mg/kg was performed in three cats. The interactive effects of almitrine and hypoxic stimulation were investigated in four cats. The interactive effects of almitrine and hypercapnic stimulation were investigated in five cats. The interactive effects of almitrine and ventilatory timing were investigated in six cats. We found that 1) almitrine doses as low as 0.1 mg/kg iv increased both HG and PHR ENG activity, with a maximum effect at approximately 1.0 mg/kg; 2) almitrine markedly increased HG and PHR ENG activity at all arterial PO2 values from 35-175 Torr; 3) almitrine increased HG and PHR ENG activity at all arterial PCO2 values from 30-70 Torr; and 4) almitrine increased the ratio of tidal volume to inspiratory time and decreased the inspiratory muscle duty cycle at normoxia and eucapnia.

Airway Obstruction↗
PubMed1985

Day-to-day pneumogram variability.

To determine day-to-day variability in respiratory pattern, we obtained 188 comparisons of pneumograms performed during two successive 24-h intervals. The respiratory pattern values calculated were total duration of brief apnea (apnea density), periodic breathing episodes, longest apnea, number of apneas greater than 11 s, and number of apneas greater than 15 s. For day 1 values for apnea density, periodic breathing, and longest apnea which were within the 90th percentile for normal infants at age 1 month, day 2 values fell outside that range in 4.3, 3.5, and 18% of comparisons, respectively. There was a systematic tendency for the day 2 values to be less than the day 1 values. For each parameter, the day 2 range was lower, the slope of the day 2 versus day 1 regression line was significantly less than 1 (p less than 0.01) and the y-intercept was significantly greater than zero (p less than 0.01). Knowledge of day-to-day pneumogram variability should be helpful in interpreting individual pneumogram results and in assessing the clinical usefulness of pneumogram recordings.

Apnea↗
PubMed1984

Electromyographic study of some accessory muscles of respiration in children with obstructive sleep apnea.

To further elucidate the pathogenesis of obstructive sleep apnea (OSA), we recorded sternocleidomastoid (SCM), genioglossal (GG), and abdominal (ABD) muscle activity, using surface electromyograms (EMGs), during 45 polygraphic studies in 39 children referred for possible OSA. For each muscle, an index of electromyographic (EMG) activity was developed, allowing an interpatient regression analysis of EMG amplitude versus highest PACO2 and lowest transcutaneous O2 tension (tcPO2) during sleep. Phasic inspiratory SCM activity was present during more than 50% of sleep time in 16 of 20 patients with OSA versus only 2 of 15 patients without OSA; SCM EMG activity increased with increasing PACO2 (r = 0.45, p less than 0.02) and decreasing tcPO2 (r = 0.51, p less than 0.01). Phasic inspiratory GG activity was present during more than 50% of sleep time in 15 of 18 patients with OSA versus none of 4 without OSA; GG EMG activity increased with increasing PACO2 (r = 0.51, p less than 0.05) and with decreasing tcPO2 (r = 0.60, p less than 0.02). Phasic expiratory ABD activity was present during more than 50% of sleep time in 10 to 20 patients with OSA versus 1 of 12 patients without OSA. These findings suggest the following conclusions: (1) inspiratory (SCM), airway-maintaining (GG), and expiratory (ABD) muscles contract during sleep-related partial airway obstruction in children; (2) augmented GG activity during periods of sleep-related partial airway obstruction suggests that pediatric OSA involves pathogenic mechanisms other than GG hypotonia; (3) expiratory ABD muscle activity suggests that some children with OSA have increased expiratory, as well as inspiratory, airway resistance during sleep.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1984

The effect of chloral hydrate on genioglossus and diaphragmatic activity.

A child presented with obstructive sleep apnea (OSA) and a near-fatal airway obstruction and respiratory arrest shortly after receiving chloral hydrate (CH). We, therefore, hypothesize that CH might selectively depress upper airway maintaining muscles such as the genioglossus and so predispose to airway obstruction. Genioglossus (GG) and diaphragmatic (DIA) integrated electromyograms (I EMGs) were recorded in four cats and four rabbits before and after hypnotic doses of CH ranging from 200-1000 mg/kg. Results were similar in both species. Peak GG I EMG decreased within 10-20 min after CH in seven of eight animals. Average peak GG I EMGs were decreased from 100% before CH to as low as 37.0 +/- 27.2% (SD) after CH (P less than 0.001). Minimum GG I EMGs fell from 47.2 +/- 27.2% of peak values before CH to as low as 16.0 +/- 9.7% after CH (P less than 0.01). Phasic GG I EMGs decreased from 53.8 +/- 25.1% of peak control activity to as low as 20.6 +/- 24.6% after CH (P less than 0.05). By contrast, peak and phasic DIA I EMGs after CH were not significantly different from those before CH administration. We conclude that hypnotic doses of CH may preferentially depress GG activity as compared with DIA activity. Selective depression of airway-maintaining muscular contraction by CH may place susceptible patients at risk for life-threatening airway obstruction and may preclude the use of CH to facilitate sleep for polygraphic evaluations in patients suspected of having OSA.

Animals↗
PubMed1984

Regulation of upper airway maintaining muscles during progressive asphyxia.

The electromyographic activity of an upper airway muscle (genioglossus, GG) and the diaphragm were studied in 10 adult and three young anesthetized rabbits during progressive asphyxia induced by airway occlusion. Results were similar for both age groups. Peak inspiratory activity of GG muscle increased more than that of the diaphragm during both the hyperpnea and gasping (P less than 0.05). The increase in GG activity during gasping was not significantly different from that during hyperpnea even though an important stimulus, arousal, was absent during gasping. During end stage asphyxia, as the strength of gasps grew weaker, the rate of loss of GG muscle activity was greater than that of the diaphragm. However, GG activity remained greater than that of the diaphragm at the time of the last spontaneous gasp. As asphyxia progressed, inspiratory duration and the inspiratory contour of integrated electromyogram activity of both muscles changed. These data indicate differences in the control mechanism of the genioglossus and diaphragm during acute severe asphyxia. Increased upper airway muscle activity seen during gasping should help preserve upper airway patency and facilitate autoresuscitation by gasping. These observations of coordinated changes in timing and activity of two functionally different respiratory muscles support the concept that gasping is a highly organized function of the respiratory centers.

Airway Resistance↗
PubMed1983

Phrenic nerve pacing in infants and children: a review of experience and report on the usefulness of phrenic nerve stimulation studies.

Nine infants and children, referred for phrenic nerve pacemakers, had measurements of phrenic nerve conduction times and diaphragmatic action potential amplitudes. In these pediatric patients, phrenic nerve conduction times varied from 2.7 to 7.8 msec, were quite reproducible, and were shorter than phrenic nerve conduction times in adults; phrenic nerve conduction time increased with age and with increasing distance between the stimulating electrode and the diaphragm. Diaphragmatic action potential amplitudes varied from 0.08 to 4.1 mV, roughly equivalent to amplitudes in adults, but were variable between patients and within patients on different days. Lower amplitudes were obtained after percutaneous stimulation than after direct phrenic nerve stimulation. Five patients underwent preoperative, percutaneous phrenic nerve stimulation. Strong diaphragmatic contractions allowed us to advise for pacemaker insertion in three patients; weak or absent diaphragmatic contractions allowed us to advise against pacemaker insertion in two patients. Postoperatively, noninvasive measurements of oxygen, carbon dioxide, tidal volume, and diaphragmatic action potential amplitudes have been used to adjust the phrenic nerve pacemaker settings. Phrenic nerve pacemakers have facilitated discharge from the hospital to a home-based ventilation program in six of the seven patients in whom they were inserted. We conclude that phrenic nerve pacing is a practical method of supporting ventilation in carefully selected infants and children. Phrenic nerve stimulation studies are useful in selecting patients for pacing and in adjusting the pacemaker settings.

Action Potentials↗
PubMed1983

Theophylline improves pneumogram abnormalities in infants at risk for sudden infant death syndrome.

To determine the efficacy of theophylline treatment in infants at increased risk for SIDS, we obtained 24-hour cardiorespiratory recordings (pneumograms) in 80 infants given theophylline in whom the initial pneumogram was abnormal. Fifty-three infants had a clinical diagnosis of near-SIDS, and 27 were asymptomatic siblings with a positive family history for SIDS. The initial pneumogram was obtained at a mean age of 6.9 weeks, and the repeat pneumogram 2.3 weeks later, when the mean theophylline blood concentration was 11.2 +/- 0.5 micrograms/ml. Theophylline treatment resulted in comparable and highly significant improvements in both groups. Among all 80 infants, apnea density decreased from 1.6 +/- 0.2% (SEM) to 0.3 +/- 0.1% (P less than 0.001), periodic breathing episodes/100 minutes decreased from 2.7 +/- 0.4 to 0.3 +/- 0.1 (P less than 0.001), and the longest apneic period decreased from 13.5 +/- 0.7 to 10.1 +/- 0.5 seconds (P less than 0.001). Findings on the pneumogram became completely normal with theophylline therapy in 87% of infants with near-SIDS and 81.5% of asymptomatic siblings. Pneumogram normalization was associated with absence of further symptomatic sleep apnea in the near-SIDS group and with continued absence of any clinical symptoms in the asymptomatic family history group. There were no deaths from SIDS.

Cheyne-Stokes Respiration↗
PubMed1982

Abnormalities of breathing control and airway maintenance in infants and children as a cause of cor pulmonale.

Respiratory control abnormalities may result in cor pulmonale. This report summarizes the clinical history, diagnostic evaluation, treatment, and outcome of 16 infants and children presenting with cor pulmonale subsequently found to be due to sleep-dependent hypoventilation. Eleven patients had cardiomegaly and electrocardiographic evidence of right ventricular hypertrophy (RVH) while 5 had only severe RVH or biventricular hypertrophy (BVH). Four infants with central hypoventilation syndrome (CHS)--absence of sleep-related ventilatory drive--had severe sleep-dependent asphyxia and resultant acute respiratory failure; all were ultimately treated with phrenic nerve pacing. One patient with alveolar hypoventilation syndrome (AHS)--a partial deficit in ventilatory drive during sleep--presented with severe pulmonary hypertension and ultimately died despite symptomatic relief with respiratory stimulants. Eleven patients presented with obstructive sleep apnea (OSA) and sleep-dependent asphyxia secondary to intermittent complete or to prolonged partial upper airway obstruction. Localized airway obstruction due to an anomalous innominate artery in 1 child was corrected by arteriopexy. Four children underwent adenotonsillectomy (T&A) with disappearance of symptoms in 1, clinical improvement in 2 and no clinical improvement in another. This unimproved patient and the 6 remaining OSA children improved dramatically after tracheostomy to bypass the sleep-dependent airway obstruction; none presently has evidence of cor pulmonale. In summary, early recognition and appropriate treatment of respiratory control disorders will improve sleep ventilation, eliminate asphyxia during sleep, and prevent the development of cor pulmonale.

Cardiomegaly↗
PubMed1982

Arousal responses in near-miss sudden infant death syndrome and in normal infants.

Hypercarbic and hypoxic arousal responses were measured in 22 normal and 11 near-miss sudden infant death syndrome infants during natural sleep. End-tidal PCO2, (PACO2), transcutaneous PO2, electrocardiogram and heart rate, and thoracic and abdominal circumference were continuously recorded. The essential behavioral criteria for arousal were eye opening and crying. For each hypercarbic arousal test, step increases in FICO2 were made until arousal occurred or until PACO2 reached 65 mm Hg. For each hypoxic arousal, step decreases in FIO2 were made until arousal occurred or until FIO2 = 0.15 had been maintained for 20 minutes. The hypercarbic arousal threshold was significantly higher in near-miss SIDS than in normal infants, 54.9 +/- 2.3 vs 48.4 +/- 1.4, respectively ((P less than 0.05). An arousal response to hypoxia occurred in only 9% of near-miss SIDS infants compared to 70% of normal infants (P less than 0.01). The level of respiratory chemostimulation required to produce an arousal response from sleep is significantly greater in near-miss SIDS than in normal infants. We speculate that deficient arousal responsiveness, especially to hypoxia, may prevent potential SIDS victims from responding appropriately to apneic asphyxia.

Arousal↗
PubMed1982

Obstructive sleep apnea in infants and children.

Twenty-two infants and children were found to have clinically significant obstructive sleep apnea. A history suggesting complete or partial airway obstruction during sleep was obtained on all patients, and physical examination of the sleeping patient revealed snoring, retractions, or OSA in 21 patients. Nevertheless, the mean delay in referral for 20 patients first seen after the neonatal period was 23 +15 (+ SD) months. Sixteen of 22 patients (73%) developed serious sequelae: cor pulmonale in 12 (55%), failure to thrive in six (27%), permanent neurologic damage in two (9%), and behavioral disturbances, hypersomnolence, or developmental delays in five (23%). Clinical and radiologic evaluations revealed anatomic abnormalities which narrowed the upper airway in 21 patients; enlarged tonsils and/or adenoids in 14, micrognathia in three,generalized facial abnormalities in three, and cleft palate repair/tonsillar hypertrophy in one. In five patients, upper airway fluoroscopy was performed and was helpful in establishing the site and mechanism of obstruction. Polygraphic monitoring was utilized to quantify the frequency and duration of OSA. Prolonged partial airway obstruction during sleep resulted in significant hypercarbia in 11 patients and hypoxemia in five. Twenty patients improved after surgery which relieved or bypassed the pharyngeal airway obstruction; two cases are pending. Increased awareness of OSA and examination of the sleeping patient should result in earlier treatment and less morbidity for infants and children with OSA.

Adenoids↗
PubMed1982

Breathing pattern and transcutaneous oxygen tension during motor activity in preterm infants.

We studied breathing pattern and transcutaneous oxygen tension (TcPO2) during episodes of sustained generalized motor activity in 18 hospitalized preterm infants. We used a newly developed quantitative method for assessing minute ventilation in infants during vigorous motor activity. We recorded respiratory air flow, tidal volume, esophageal pressure, TcPO2, and electromyograms of various muscle groups. We observed a distinctive pattern of breathing ("exertional breathing pattern") that was invariably associated with episodes of "squirming" motor activity. This breathing pattern is characterized by reduced minute volume, intermittent Valsalva maneuvers, and obstructed inspiratory effects (obstructive apnea). Episodes of squirming with the accompanying altered breathing pattern were usually followed by a decrease in TcPO2. These episodes occurred spontaneously or could be induced by sensory stimulation. They appear to be a significant cause of obstructive apnea and TcPO2 instability in hospitalized preterm infants, and were responsible for 30% of sudden decreases in TcP[O2 of 10 mmHg or greater.

Heart Rate↗